out-of-band

1. communications The exchange of call control information

on a dedicated channel, separate from that used by the

telephone call or data transmission.

2. Sometimes used to describe what communications people call

"shift characters", such as the ESC that leads control

sequences for many terminals, or the level shift indicators in

the old 5-bit Baudot codes.

3. In personal communication, using methods other than

electronic mail, such as telephone or snail-mail.

4. software Values returned by a function that are not in

its "natural" range of return values, but rather signal some

kind of exception. Many C functions that normally return

a non-negative integer return -1 to indicate failure.

This use confuses "out-of-band" with "out-of-range". It is

actually a clear example of in-band signalling since it uses

the same "channel" for control and data.

Compare hidden flag, green bytes, fence.

[Jargon File]

(2001-04-08)